Apparatus for measuring fluids for turbidity, color, and other characteristics



- 41644,'305 ff-- Oct. 4,1927. W G. EXTON .3 y

APPARATUS FOR MEASURING FLUIDS FOR TURBIDITY,

COLOR, AND OTHER CHARACTERISTICS Filed June 11. 1925 s,shams-s119181 i BY 'l 0 3 3 d. 4 0D` al.

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ocr. 4.-, 1927.

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ma/M r ATTORNEYS.'

APPARATUS FOR VM EXTO EASURING FLUIDS FOR TURBIDITY, COLOR, ANDkOTHER CHARACTERISTICS' Filed June 1l. 1923 s sheets-sheetl 5 l I y 4 l f zy, L

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ll/ LA, 26. l @I U 2V 'I l aguil r4 INVENToR. l I $5565@ Patented Oct. l4, 1927.

WILLIAM. e. Extron, on una' Yoan, n. Y.

. aai

rares) APPABTUS FOB MEASURING FLUDS FOR TBIDETY, COLOR, .AND O'lfEili;`

Y CHARACTERSTGS. 'I

vApplicationfiled .Tune 11, 1923. Serial No. 644,602.

This invention relates, generally, to a 'novel apparatus or instrument for measure ing turbidities, colors and other characteristics of fluids by optical observation'. i

The inventionv has for its principal object to provide a novel'construction of optical instrument'adapted to permit direct readings of fluids for cloudiness, color and other characteristics Without necessity for using standards for comparison; the said instrument being adapted to operate either .by transmitted light, that is by light transmitted through the fluid examined, or by reflected light, that. is light reflected from substances suspended in the fluid Which give rise to itsv turbidity, it being substantially agreed by investigators of the physics of turbidity, that denser solutions are. better measured by transmitted light, While solutions of slight concentration are better measured by reflected light. To this end, therefore, the novel instrument possesses a means' for controlling the passage of lightfrom a suitable target to an optical viewing device. or eye-piece,and a means for interposing acomparatively small quantity of the fluid to be measured between said optical viewing1 device or eye-piece and the target. The light source and controlling means may be 'so manipulated or arranged asv to illuminate the target by light 'transmitted from beneath the latter, or., by an incidence grazing light entering the side f and passing laterally through the target, or

by light reflected upon the target from the substances suspended in the fluid. The instrument is further provided'with means for varying the depth of they fluid toproduce a predetermined visual effect or appearance of the target when viewed through the fluid and illuminated byv either transmitted or incidence grazing light, which indicates'the measuring ypoint readable on a scale arranged to vary as the depth Vof thev fluid varies.` rlhe instrument is alsov ,provided with means for varying the quantity of light reflected y.from the suspended.substances in the fluid until a. predetermined visual effect or appearance of the illuminated target, when viewed through the fluid, is obtained, which indicates. the measuring point readable on a scale arranged to vary as the quantity of light varies. Various combinations of transmitted and reflected' light, kvcon-l trolled as yalcove mentioned, may be em-j ployed. 'l

rl`he invention has for a further object to".A

provide instrument of thekind described, in which the control of light from the source and through the instrument is such that interfering stray light and reflected light is reduced to a negligible minimum, so V.thaty the accuracy and dependibility of the read-V ings obtained are assured. y

Other'obj'ects of' this invention, not at vthis time more particularly enumerated,-Wil'lj'be detailed description of the samarlhe Vinvention is clearly ill strated in the accompanying drawings', in vvhich :r-

Figure l is a verticallongitudinal section of the novel instrument made accordingn to`r and embodying the principles of this inven' tion; FigureQy is a transverse vertical longitudinal section, takenon line 2 2' in Figure l; Figure 2 is a horizontal section through the fluid cup', taken on lineQL.- e" in FigureV 2'; Figure 3 is a. side elevation of a y"portion of the instrument; Figure el vis a transverse section, taken on line @-4 Figure il.; Figure 5y is'anothertransverse section,1 taken 'clearly' understood from the following on line 5-5 inFigure l; and Figure 'is'a fragmentary front elevation of a portion of the instrument. Figure 7 isl a face: orplan Similar characters of reference areemploy'ed in all of the hereinabove described` views, to 4indicate corresponding parts'.l

Referring' now to said `draufvings=,y the reference character' l indicates a base-upon which is supported a casing orcabinet pro-V viding 'an interior' `light-proof `chamber 3. The top end Wall of said casing 'or' cabinet soi" 2 is provided With an opening il.V Fixed .l

uponsaicf top end Wall, 'so as to` register over said opening 4f, isa tubular barrel-5, in which is supported an optical viewing device or eye-piece consisting' of aV focusable lens-holder 6" having K suitable 1 lensesff 7 il: i, fli) Areo adapted to produce a magnification of desired power.Y

VThe'lower or or `cabinet provides a reflector chamber 8 inv which Ais situated a reflector member 9 disposed at the proper angle to reflect light Y upwardly through the main chamber" 3 to- -ward the optical viewing device or eye-piece.

" f lower guide-grooves. 10".

FiXedto the interior sides of said casing or cabinet 2, above said reflector inember'9, are

Va pairof opposed transverse guide-blocks .10.see14`1gure 2, having upper guide-grooves 10.', intermediate `guide' grooves 10A and Slidingly and removably supported by` said upper guidegrooves 10. is -a cup-supporting plate 11 I `having an opening 12 the marginal portions .of which are vformed to provide a cup-seat 13.f Slidingly and removably. supported by `said intermediate guide grooves 10 is a target-supporting plate 14 having` an opening 1 15 the marginal portions of which are formed r to provide a target-seat 16. The space 17 intermediate saidcup-supporting plate. 11 .and 4said target supporting plate 14 provides an incidence grazing light chamber, the purypose of which will he subsequently more fully set forth.; Slidinglv and removably supported by said lower guide grooves 10 is an auxiliary supporting plate 18 having an l openingf19 the marginal portions' of which -are formed to providel a seat 2O for auxil- .iary light yfilters or targets as occasion may require.V Arranged in the front wal] of' the casinar Vor cabinet 2 is a removable door 21, see Figure 6. which when. open permits access tothe main chamber 3. reiiector `chamber' 8 vand to the above-described supporting kplates 11 14 and 18, whereby the Y latter *maybe withdrawn to place thereon f-orfremove therefrom the various elements they are designed to support,` The respec- Vtive openings of the severalsunportinn;

plates 11. 14 and 1'8 are all verticallyalined Lw'ith one another and with the optical view-- ing Vdevicezor Veye-niece, so thatlight reflected from the reflector member` 9 will be i transmittedA therethrough and through .the 'nelements supportedthereon to said optical viewine` device oreye-piece.

' .suitably secured upon the back of the casing or cabinet 2 in proper location are horizontal but.l vertically spaced apart cuideblocks 22 which are adapted. te slidincrlyv support acover-slide23 operating to close an opening 241 inthe casi-ng or cabinetwall which y light chamber 17.V and to slidinglv support a Y second cover-slide 25 operating to close `an opening 26leading into said redentor chamleads-` into the incidence The reference character 27 yindica-tes a fluid holding cup, preferably made of glass,

the exterior side of which is l@round to provide a longitudinal panel providing al plane bottom'end of said casing .grazingsurface 27 extending the full length of the cup. The lower end of said cup is closed by a transparent bottom member 28 made of optical glass. Connected withV the upper open end ofy said cup is an annularly enlarged portion 29 which provides va basin 30 for receiving the .overflow of fluid displaced.

from the cup when an optical plunger torbe .subsequently described is lowered into the sameduring the operation of the instrunient. When normally placed within the instrument the cup 27 is supported Vby its lower end in the. cup-seat 13 of the supporting plate 11. so that its transparent bottom is registered over the openingV 12 of the latter. lThe main body ofthe cup belowV 1 the basinv 30 is preferably ymade of `'such dimensions that it will hold when full a column of fluid 100 millimeters lin depth.

Mounted on the inner sidev of the front wall ofthe casing or cabinet 2 and-off-set to one side of the doorway 21, are a pair of vertically disposed guideway strips 31 which slidingly support for up vand'down movenient.. a slide-plate 32. Secured upon the slide-plate l32 is a longitudinal toothed rack 33. Journaled -in Abearings 34 and 35 is a. spindle 36 which extends across said slideplate and which is provided with a pinion 3"("wliichV operatively meshes with said rack One end of said yspindle 36 projects eX- teriorly from the Yside of the casing or cabinet and is provided with a knob or fingerpiece38 for rotating said spindle and pinion V l Vto transmit through saidrack either an upward or vdownward movement tosaid slideplate, as may be desired. Securedto the upper end. of saidsli'de-plate'is `a laterally projecting bracketV 39, havingr an internally lthreaded'ring 40 at its free'. end in which f is. threaded the ferrule 41 to which secured a downwardly projecting I optical plunger, the latter being so positioned' as tobe axially alined between the cup 27'and the optical viewing device orreye-piece ofthe instrunient. Said optical plunger may be made in various ways so uthat* light will pass,

lengthwise therethrough. Preferably the same consists of a glass tube 42 closed at .its

bottom .end by a `bottom-piece 43 made of Vtransparent optical glass.y andV preferably closed lat its upper end by a cover-piece 44 also made of optical glass, Vand which pre- Qveiits dust from entering and accumulating` Vthe plunger will also move correspondingly l.up and down relative to the 'eup'27 so that it may be entered intoor retracted from the interior of the latterto vary the depth of the 'column of fluid exposed between the-bottom -ot the cup and the bottom ot the plunger.

Preferably the Yslide-'plate is .arranged so as tobe capable of a movement inexcess of 100 millimeters, the Zero position being that in which the optical vplunger is in lowermost position ,engaging the bottom ofy the cup, thus permitting av rea-ding or measuring of Vthe depth of fluid between the bottom of the cup and the lower endl of the plunger. To the end that sucli Imea-surements may Vbe quickly and easily read the yslide-plate. 32Vis graduated toprovide'a 109 millimeterv scale (see Figure 6)v ivhich is read through an opening 46 provided in the front Wall of said casing or cabinet 2 over Whichthe slideplate and its scale moves,` the reading being` made with reference to a xed mark etclie d at one marginal side of said opening,l 46.'` It will thus be apparent that the depth of the column oit uid intermediatev the en d of the plu-nger and the bottoni oit the fluid cup may' be increased or decreased at will by raising or lowering the'plu'nger, and that the scale will rise and fall proportionately tol the plunger movement to yalter Ethe reading` oi"- the scale as the depth offluid alters.

Provided in the rear Wall-of the casing or cabinet 2 lis an 'opening 4'? directly opposed to thecup 27 and corresponding in height Vto the height 'of the cup, that is7 in the present case 'being 100 vmillimeters. The plane surfaced panel 27 fof the cup faces this opening 47. Arranged upon the inside otr the reary Wall', and respectively disposed on eitherzside of said openingr 47 are guidevvay members 48 which slidingly support for up and ldown movement a. vshutter 49. Fixed on said shutterr49 is a longitudinal toothed rack 50. Journaled to extend across` said shutter 49 is 'a spindle 5l `'which isl provided 'with a pinion 52 to' operatively mesh vWith said rack 50, One. end ot said spindle 51 projects exterioriy fromr the lside oi'-the casing or cabinet, and is provided with a knob or finger-piece 53 for rotating said spindle and pinion to transmit through' said rack either an upward or downward movement to'sa'id doorlslide, whereby the opening` 47 may be closedor' opened to the'` desired degree. In order to permit ofthe` measurement of the amount of openingl provided by a given adjustment of the shutter 49, the

latter is graduated to pro-vide a 100 millimeter scale (see Figure 4) which -is read through an openingr54 provided in the Wall of' said casing or cabinet'Q over which the shutter 49 and its scale moves, the reading 'being made with reference toa fixed mark etched at one marginal side ot' said opening 54. vThe closed position ot the shutter 49 establishes the zeromark or positionofthe scale. y.

Arranged upon said base'LJn the rear ot said casing or cabinetl 2, are"slideivay'mein-A bers: 55 upon Whichfis mounted 'avfcarriage 'plate 5d Vrimvable towardl and away'v from ysaid casing' or cabinet 2L Fixed-onsai'd carstandard 58 which is rotatably adjustable on, .y l

its vertical axis, but is capable Q being fixed .in adjusted position by a lozlrnut mcans59.

cooperatinnjw'th the same andsaid bearing ring.'l Said socket-standard 58 is` provided f Withfav suitable electric -lampsocket 58 in which is connectedV an electric `filament lamp 60 oi special design. The longitudinalaxis of saidvlamp 6U, as thus 'mounted,j and the `axis through the'optical viewing device, cup 27 vand associated elements in 'the casing" or cabinet 2y are parallel-and alined in the same plane. By r'otzdingg'the socket standard 58 the lamp-filament maybe adjustedin position so as to be al'inedin the same plane. Suitabl-y securedv to the free'endof said solret standard 58 is alamp-hood 6l yprovided With a longitudinal slotv or openingj2ivhich faces the casing or cabinet 2. `The lainp 60 constitutes the/light .sourcey oi the instrumennjand the samef maybe adjusted."

toward` or away trom'the casing or cabinet 2 to secure the desired' degree" of light in-y 1 A tensity and photometric adjustment or light relative to points -Where the light is permitted to enter the casing; 'or cabinet.' A scale 55 .1 attached to a slidewayjmember '55, With.

Which the carriage-plate cooperates .Wills-permit a measurement of theainount ofaldjustment lof the lamprel'ative to the casingon Y vcabinet. j

livill tirstbrie'iiy of the instrument-When measuring; a iuid ci comparatively heavy turbidity'. y As above j mentioned for such fluids the instrumentv explain 'the functioningV f is preferably 'adj usted for the transmission of y light directly'through a target and then by 4Way of the interposed column otV fluid ktothe optical viewing device-or eye-'piece'. Under such conditions the eover`-slide 23 closed to exclude light ro'm the incidence f grazing light chamber 17, and the shutter 49 is closed .to vexclude lateral lifrl'itfrays `from' 'the -fluidA iup Q7', While the cover-slide is opened to permit light from the properly 'adjusted n Y. lamp'Oto fall uponthe rellectormember 9.

The fluid to be measured is placed in the cup 27` and the optical plunger israclred downto the Zero'position in vcontact with the bottom ofthe cup.

upwardly therethrough. :A target as 63 Vpossesses a hair line 63 A suitable target is thenplaced beneaththe cup9 so thatlight will be reiiected iis etched upon its surface. or atar-get (i4 (see Figure 8) may be employed 'which may con,-

'sistot' kopaogue silvered ,Qlass'having a trans` parentv line 64.` or other symbol thereon, orl *any other desired character orv target.

f, lThe operator now :applies his eye tothe vopticalviewing device or eye-(piece, which vhas been focused, While the plungerls down tozero position, upon the lineor symbol .of the target so that a clear definition of the same is attainedrk The operator Ynext racks Y the plunger up and down to adjustorvary the depthfof fluid interposed between lthe same `and the bottom ofr the cup'27 until i suchdepth of the Huid is attained that the `V vdefined line orsy'mbol .ofthe target is obscured, that `is untilvthe point is reached at .whichythe turbidity of the fluid intercepts thellight rays .passing throughl the target marks or symbols.` Y' This point establishes the reading` point-and the-scaleu of the slideplate132ris read, and compared with a table vof predetermined andestablished standard i letched line or other symbol.

f Y yCertain characters of'fluids may readings, soL that the amount of turbidity possessed by thejfluidtunder examination is directlyobtained by such reading.V .y

bebetter measuredfor-turbidity by a variation of the yabove' operationjand the method entailed thereinT This variation consists in' employ.

ing aj transparent glass target of substantial thickness .having on vits upper surface an Such va target is shown'in Figures I, 2 and Tof the drawings, When using this target,:light may be V v,excluded from the reflector member 9 by c closing'the cover-slideQ,y but admitted to the y l lfchamber 17 by opening the cover-slide v23.

` The" light thereupon traverses the target `laterally andV at right `anglesto the axis of view fthrough` the instrument.' The target field willjthereforeremain dark except wherethe i 'i lighty grazes the incidenceof Vthe etched line "or/symbol on the surface Vof lthe target,

thereby causing a reflection therefrom which Y 'renders the line or symbol bright or luminous against the ydark field of the main'target surf face. The plunger is racked up and down 'until the light of the luminous line or sym- I bol is obscured or intercepted by the depth of fluid interposed, thus .establishing a read- V-ing point` much in the same manner as already above described; ,l Y

1A variation of the optical method-involved in. .'theV ,use of my novel instrument, and Y adapted to the' examination of yfluids through y `Way wide range of turbidity, consists in employing either incidence grazing light or 1 transmitted light directed upon thel target `in conjunction 'or combinationwith'light reflectedb from the particles in suspension'in the fluid; under-such circumstances the fluid i inL the cup being illuminated by laterally i traversing light, in the naturegof va Tyndall l' beam, which is admittedv to the cup chamber 3, by openings the shutter 49 so` that light i from the lamp v may strike through the plane surface i'fofthecup andv illuminate )the particles in suspension 'in 'the fluid con' tent thereof. In practicing thismethodthe,

plunger 42 is racked down to zero position Y in contact'with the bottom of the cup and the eye-piece is focused onv the target which is illuminated by transmitted light from the reflector member 9 or by incidence grazingV light 'admitted 'to` kthe target chamber 17. The shutter 49 is fully opened. The turbid yfluid to be measured is now kpoured'into the cup. The plunger is then racked yup admitting kthe Tyndall beam through Vthe cloudy fluid until theamount of light re# flected from the vparticles in suspension in the fluidV ymatches the illumination of the target or obscures the target yilluminated by incidence grazing light, thus producing practically a photometric match. When such condition is established, the reading point on the plunger slide scale is reached. In some cases the above method may be varied by placing the plunger at a predetermined position to establish a predetermined depth lof fluid in thev cup, thereupon, admittingla varying quantity of light by raising or lowering the shutter 49 untilthe visual effect Y upon the target isv obtained, .the reading .then being made on the shutter scale.

F or exceedingly line `turbidities another method involvesthe use of a high powered eye-pieceof increasedv magnification, soadjusted as to resolve the very fine ruling 66 of a transparent target such as shown in Figure 77a. In order to avoid difficulties connected with focusing with increased magnifications, the plunger. 42 is set atlthe 109 millimeter mark and the eye-piece is then ico,

focused on the target, and then the'Tyndall c beam is regulated by raisingl and lowering 'the shutter 49, until the amount of light reamin'ed, the plunger being racked or ad-V justed until `all light is excluded from the eye-piece except that which is absorbed by -the color of the fluid under examination.

In practicing this method I make use of one of a series of analyzing targets, such as shown in Figure 9, which possesses a plu-v ralityof sectors providing a variety of light filters permitting differentA transmissions. These-analyzing targets are viewed through thefluidunder examination to ascertain' which filter provides the proper comple.V

mentary color filter for that particular fluid.

This fact being ascertained, a determination 13,0.

all other light :trom the interiory ot the casing or cabinet.`r The plungeris novv racked upfand'down until a point isreached Where the depthoil lfluid examined absorbs or inter- 'cepts all light vpassing through the filter panelVr of thefdet'ermination' target; .so that said panel matches theblacl: or light eX- cluding ield of the latter, thus establishing the reading point on thev plunger scale. The'marginalYclear glass field of the target permits a :continued light transmission through the fluid under examination, so that the absorption of'iightpassing through rthe lter panel is not at all dependent at any stave upon `the threshold ot vision.

f" am aware that 'somechanges may be made in the several*arrangements and combinations fof the devices and parts, as well asin vthev details 'of the' construction of the same, Withoutfdeparting from the scope of .thisf'i'nvention as set forth 'in the 'foregoing speciitica-tion,l and Eas defined inthev appends]L claims.- Hence, l' do not limit my-invention to the exactarrangements and combinations of the `various devices and parts las described injsaid'specification, nor dol conline myself Vto the exact details of 'the'. construction oat Y said parts as illustrated'in the-'accompanying drawings. v Y v `l-claim:- 'Y or '1. An instrument of the' kind described,

comprising a light-proof cabinetrhaving a viewing aperture at its'upper end;-I a 'lfluid cup having a transparentV bottom vertically alined beneath said aperture; a testingelement alined beneathisaid fluid cup; la source of illumination mounted exterior-ly of lsaid cabinet; selective means connected with said cabinet operatable singly or in combination for controlling the admission thereinto of light :trom saidilight source toilluminate the testing element yfrom beneath or laterlallyby incidence grazingslight, and to illuminate the content oli s-aidiluid cupby a Tyndallbeam, vand inea-'ns' ior varying and measuring the depth `of the content oi" said fluidv cup. l 1 f 2. An instrument of the'ltinddescribed, comprisingy a light-prooi1 cabinet; a focu'safble optical viewing device connected" With lthel'u'pper end of said cabinet; aufluid cup` 'having' a` transparent bottom vertically 'alined beneath' said voptical vieiving'dev-ic'e;

v-atestn'g .element alined beneath said luid cup; a source of illumination-mounted exteriorly of said cabinet; selective means com nected Withisaid cabinet operatable singly"r or in combination 'for controllingfthe fad-v mission tliereinto of light l'ronisaid light source to illuminate the testing element from beneath or laterally by incidence. grazing light, and to illuminate the content .of said fluid cup by aflyndall beam; and. means 'orvi varying and measuring the depth of they contentl of said fluid cup. f

8. An Vinstrument 01 the kind described,y

comprising a lightfproof cabinet, a ocusaf ble optical viewing device connected With the upper end ot said cabinet; a fluid cup having a transparent bottom vertically alined beneathsaid optical viewing device; v aV testing element alined beneath said {lui-d cupi; a source oi illumination mounted exe teriorly of said cabinet; selective means lcoml nected With said cabinet operatable singly or in combination for controlling the admis=y sion the'reiiito ot light from said lightv source to 'illuminate the testing .elei'nentfrzom`r be:r neath orlaterally by incidence grazing light, and to illuminate the contento't'said tluid cup bya Tyndall beam; an optical plunger l vertically movablel between said optical `viewing device and saidl fluid cup; means for actuating said plunger to vary the depth oi" liuid'in said iiuid cup; and means cooperf Vating Withsaid'plunger actuating means for measuring the depth -ot' tluidV intermediate` the bottom` of said luidy cup-and said plunger.

fl. Aninstrument of the hindfdescribed,v y

comprising a lightfproot cabinet; a focusavble optical viewing-device .connected With the upper end 'oi said cabinet; a fluid cup having a transparent bottom; means for supporting said liuidjcup in vertical allinement beneath said optical viewing device; a testiiig element or target; means for support? ing said testing element or target in vertical alinement beneath said fluid cup; a reflector member beneath said' testing element vfor target; Ya light source' `enteriorly disposed relative to said cabinet; meanstor adjusting said light sourcefrelative to .said cabinet; said cabinet having aiiopening intermediate said light source and said reliector'member;

a cover-slide associated with said opening; said cabinet having la second opening intermediate said light source and said testing element or target adaptedto admit incidence grazing light to the' latter; a second cover- .llOv

slide associated With Vsaid vrsecond opening; y

stantially corresponding in height 'to they V'height of said fluid cupand Ysituated interjmediate the latter .and said light source; `a

shutter for said t-hird opening; meansor actuating said shutter; meanscooperating with said shutter actuating ymeans for meas uring the amount of lightadmitted through p said-third opening; vand means for varying andjmeasuring, the depth'ofthe content of said lluidcup'... n i l f5.1An instrument of the Vhind described,

v comprisinga light-proof cabinet; a focusablegoptical .viewing device connected With the -upper endof said cabinet; a fluid cup -having'a transparent bottom-V; means for vsupporting said/fluid cupin vertical alinementv beneath said optical viewing device;

i aY testing ,elementor ktarget in vertical aline-v ment beneathsaid fluid cup; a reflector memw ber beneath said testing element or target; aV light source,'exteriorlyy disposed relative Vto said cabinet; ,means for adjusting said light source relative to said cabinet; said cabinet havingfancopening intermediate said light sourceand vsaid reflector member; a coverslide associated With -said opening; said cabinethaving Ia second openinguntermediatesaidflightV source and said testing element `or targetgadapted to admit incidence f grazing light tothe-' latter5a second coverslidey associated with said second opening; said cabinet having a thirdopening substantially Corresponding infheightto the height ofsaid'fluid cupand situated intermediate thevlatter and vsaid'light source; ashutter f for said thirds-opening.; means for actuating i shutter` actuatingmeans yformeasuring the 'saidl shutter; means cooperating With. said amount offlightk admitted through said third Y opening;. an optical plunger vertically mova ble betweeny said optical viewing device and `said fluid cup';means for yactuating said .plunger torvary vthe .depth of fluid in said fluid cup; and means cooperating with said plunger actuating means for measuring the depth of fluidy intermediateV the bottomv of 4o saidQfluid cup Sand said plunger.

6. An instrument ofthe kind. described, comprisinga light-proof cabinet; a focusable optical viewing device connected With the {upper'end of said.v cabinet; a transparent fluid cupalined beneath said viewing device;

means for varying and measuring the depth of the contentof said fluid cup; a target; *means for supporting said target invertical alinement beneath saidjfluid cup; an external light source; a reflector member beneath said target; and saidcabinet having an open- Ling intermediate said light source and said -reflector `member'providedwith means for opening and closing fthe'same.

' g 7. instrument of the kinddescribed, comprisinga. light-proof cabinet; a focusable optical viewing device connected With .the upper end of said cabinet ;atransparentl ,fluid cup aligned beneathl said viewing ldevice; means' for Yvarying and measuring the vdepthl ofthe content of said fluid cup; a

. ytarget'; `meansfor supporting 'said target in v.vertical alinement beneafthlsaid 'fluid cup;

.-1aneXternal-liglit source a reflector vmember fbeneath said target; said cabinethaving an openingintermediate said light `source and said reflector member provided with means for opening and, closing the same, and said cabinet having a light admission opening iii-y termediate said fluid cup Iand said light source corresponding inlength to the length,

of the former; and adjustablemeans for opening and closing said Vlight admission opening having means for measuring the amount of' adjusted opening. Y

8. An instrument of theA kind described, vcomprising a light-proof cabinet; la focus able optical device connected With the upper 'i end of said cabinet; a transparent fluid cupv Y. I

so n

alined .beneath saidviewing device; 'means for varying and measuring the 'depth ofthe content of' said fluid cup; a target; means for supporting said target in vertical alinement beneathsaid fluid. cup; an external light source; said .cabinet having an opening intermediate. said target and saidI light source to permit incidence vgrazing light to illuminate said target; and means for open-Vv ing and closing said opening.

9. An instrument of thefkind described,`

comprising alight-proof cabinet; a-focusable optical viewing device connectedv With the upper endvof said cabinet; fatransparent fluid cup alnedbeneath said viewing device;

means for varying and measuring the depth fof the content of said fluid cup; atarget;

means for supporting said target in vertical alineinent beneath said fluid cup; vanjexternal light source; said cabinetrphaving. an-

kopening intermediate said target and said light source to permit incidence grazing light to illuminate'sa'id target; vmeans for opening and closing said opening; and-said cabinet having a light admission opening intermediate said fluid cup and said lightsource corthe kind described,

plunger-movable into saidcup, vactuating means for raising and lowering said plunger to vary the depth of the, content of said kfluid cup, means cooperatingl Withv said plunger actuatingmeans forlindicating the adjusted depth of thecontent. of said fluid cup, a target beneath said uid cup; alight source, means for admitting light tosaid target to illuminate the same, and means for vadmitting Vlight in the form of valvvTyndallY said Vfluid cup andl its beam to traverse content, Y y Y Y 211, Aninstrument of the kind described, comprising a light-proof cabinet; a transparent fluid cup yin said cabinet, a transparent e plunger f movable into said;4 cup, actuating 'f means for raising and lowering said plunger 139 `v to vary the depth of thecontent ofsaid fluid cup, means cooperating With said plunger actuating means for indicating the adjusted depth of the content of said fluid cup, a target beneath said fluid cup, said targetcomprising an opaque body Within.

the lield of which is etched a light transmitting target mark, and means for illuminating said target. Y

l2. An instrument of the kind described, comprising a lightproof cabinet, atransparent fluid cup in said cabinet, a transparent plunger movable into said cup, actuating i this 7th, day of means for raising and lowering said plunger to. vary the depth of the content of said fluid cup, means cooperatingwith saidy plunger.:

ltarget beneath said liuid cup, means for illummating said target, and means for illuminating the content ot' -said fluid cup by a laterally traversing or Tyndall beam.

' vIn testimony, that I claim the invention setforth above I have hereunto set my hand June, 1923.v n VILLIAM Gr. EXTON. 

